Class III Malocclusions -In Class III malocclusions, the lower incisor edges lie anterior to the cingulum plateau of the upper incisors -Class III malocclusion is found in about 3 percent of children -Frequently it is the associated skeletal malrelationships and the prominence of the chin as much as the malocclusion itself that is of concern to patients and their families. Occlusal Features: -In mild cases the incisors meet in an edge-to-edge relationship, when there may be an anterior mandibular displacement to obtain a posterior occlusion. -In more severe cases there is an appreciable reverse overjet. -The buccal segment relationship may be class I and it is unusual to find a full premolar width of mesiocclusion. -The upper arch is often narrow as well as being short, and the lower arch is broad; thus crossbites are common. -Where there is a more severe discrepancy in arch widths there is a bilateral crossbite. - The upper arch is frequently crowded because it is short and narrow, while the lower arch may well be spaced. Severe lower arch crowding is not common. Skeletal Relationships: -There is usually a Class III skeletal pattern Facial Growth: -In Class III cases, facial growth is often unfavourable: the usual tendency for the mandible to become more prognathic relative to the upper face is adverse. - Vertical facial grwoth increass any tendency to skeletal open bite, particularly where there is a high maxillary mandibular planes angle and a tendency towards a posterior growth rotation of the mandibular. Different facial types associated with Class III malocclusions. a. The anterior intermaxillary height is large and there is an associated skeletal openbite. This type of facial pattern can be expected to grow primarily vertically. b. The anterior intermaxillary height is reduced and the overbite is deep. Treatment Objectives: Correction of the occlusal malorelationships with orthodontic appliances is possible only in the milder malocclusion, although these do form the greater proportion of all Class III cases. In severe cases, surgical intervention is required if the malocclusion is to be corrected.
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